Typical and atypical repetitive motor behaviors in young children at risk for severe mental retardation.

A sample of children, ages 1 to 3 years, identified as being at risk for severe mental retardation, was observed in a semi-longitudinal study to assess their pattern of typical repetitive movements topographically similar to aberrant, stereotyped behaviors and to determine the prevalence of atypical stereotypies at this age. Frequency scores, collected using a partial-interval time-sampling procedure, were analyzed on three variables (age, time of measurement, and environmental condition) using repeated measures analysis of variance. Results were discussed in light of similar studies of infants without disabilities.